Polymorphing is the changing of a creature's shape through magic, available via several spells and class feats. Polymorphed creatures retain their own minds but have new physical forms, with a new racial type and often with preset strength, dexterity, and constitution scores. Any ability score that is not overridden by the new form will be affected by the racial modifiers of the new race, losing any racial modifiers of the old race (but this will not be reflected on the character sheet). In addition, anything dependent on racial type (such as favored enemy) will be with respect to the new race for as long as the polymorph is in effect. For example, the bonus from battle training vs. giants is lost against a giant polymorphed into something else, but it is gained against any creature polymorphed into a giant.
The new physical form of a polymorph is realized in the game by a new appearance and a new portrait. Some polymorphs also change the soundset (and this is the only way to change a creature's soundset). Many polymorphs provide creature weapons to go with the new form, while others may provide a standard weapon that cannot be unequipped for the duration of the polymorph. Other possible benefits of a polymorph – all depending on which polymorph is being used – include a spell-like ability (or three), a temporary hit point bonus, and a dodge armor class bonus. In addition, any item property that can be placed on a skin item could be included as part of the polymorph.
On the downside, polymorphed creatures are unable to use most items, aside from potions. In addition, equipped items are unavailable while polymorphed, resulting in a loss of their properties. The most hazardous of these losses is the loss of a constitution bonus, which may kill an injured character. An irritating loss is the loss of bonus spells, as this will clear the lost slots (This has been fixed in the enhanced edition, bonus spells are retained). For older versions this can sometimes be mitigated by first casting a spell, such as fox's cunning, to boost the relevant spellcasting ability before polymorphing). As a special case, feat-based polymorphing does allow some properties from equipped items to be retained in the new form. However, even when properties are retained, they are lost for a split second while polymorphing, so the side-effects still occur. (Again fixed in the enhanced edition)
When a polymorph ends, ability scores, race, and items revert back to normal, and any remaining temporary hit points are lost. This has the usual consequences with one exception: the change in base constitution (if any) will not kill the creature. Instead, the creature will have a minimum of one hit point when the polymorph ends (unless the creature was already dead or dying). However, if a constitution buff is ending at the same time (typically when resting) then the loss of the constitution buff occurs first and can kill the creature before the polymorph is removed. This means a polymorph can be used to prevent a character from dying when resting with low hit points and a constitution buff, but only if the polymorphed creature could survive the loss of the buff.
Most polymorphs can be canceled by selecting the bottommost option in the character's radial menu. However, the module builder can suppress the cancel option when desired (through the second parameter to
Canceling a polymorph takes only the time of the animation, so it is possible to perform another action (such as casting a spell) the same round.
Player characters when polymorphed are blocked from normal spell-casting. They may use spell-like abilities and feats that mimic spells, though. Note that parts of the radial menu may be inaccessible, so feats that might otherwise be activated that way (such as epic spells) must be activated using quickslots.
In addition, a polymorphed creature is blocked from horse riding, and a creature currently riding a horse is blocked from initiating a polymorph (possibly unless the spell in question has been customized). The standard implementation of the latter restriction has the side-effect of often causing a character to become unable to make attacks after the first polymorph of a game (per module or server reset). This can be worked around by canceling the first polymorph and initiating a second one. Alternatively, the "Remove PC Properties" override from the Vault eliminates this problem.
There is a bug in the game that causes a polymorphed character's temporary hit points to be reapplied each time a (saved) game is loaded while polymorphed. These reapplications stack without limit, allowing sizable hit point totals for players who abuse the bug. Furthermore, only a single application of these temporary hit points is removed if the polymorph is canceled. Additionally the game does not retain what items you had equipped pre-polymorph in savegames and instead tries to re-equipped them after the polymorph ends after loading a save game, this has various side effects like losing bonus spell slots, and is not fixed in the enhanced edition.
The available polymorphs are defined in